On 22/02/2017 19:01, newshound wrote:
On 2/22/2017 5:06 PM, John Rumm wrote:
On 22/02/2017 13:19, DerbyBorn wrote:

That is a mess. Those places where I see PTFE poking out, look to me as
if they were intended to have a fibre washer fitted between flat faces.
You might get PTFE to seal, but only if you can get a regular layer of
PTFE around the threads and of just the right thickness, which is
unlikely - so it will leak.


What I was thinking (Looks like a tap elbow)- I would be inclined to
take
the photo to a decent Plumbers Merchant and get the correct fittings for
the job.

Althought PTFE on the tread is not the solution, it should be wound
on so
that screwing the fitting will tend to tighten the tape - and not
push it
out.

If one were going to try and get a seal on that with PTFE you would need
to be quite careful with the winding of it - basically creating a taper
shape[1] on the thread with the tape, so that the "screw in" resistance
increases sharply as the stub penetrates further into the female thread.

e.g. you start with say 4 or 5 turns toward the tip of the thread and
work up to many more (10 to 20) laid up toward the back of the thread) -
winding the tape on "edgeways" so that it folds up helps build thickness
faster.

Agreed.

Another technique with it is to roll the tape between your fingers to
make "string" and then wind that helically into the threads. You can
also, with care, fabricate a replacement for the fibre washer on a tap
connector by winding several turns of this PTFE "string" on to the step
which should take the washer. Emphatically *not* recommended as a
permanent fix, but in the absence of proper washers I have done it a
couple of times for friends on a Sunday evening, when miles away from my
toolboxes. Most of these include a tobacco tin containing some of these
washers, fuses, fuse wire, and a couple of chocolate blocks. And bits of
red and green/yellow sleeve.

Yup, I found that I can quite reliably get a seal on parallel male and
female threads using the tape trick. Last time was when I wanted to test
the soundness of the rads after multiple mods and changes. I needed to
bodge a way of connecting my pressure gauge to a rad top connection. The
gauge made a good seal on to the end of a service valve with its
internal washer, then all I needed to do was get a service valve to seal
on the top boss of the rad (having removed the bleed valve). Application
of PTFE as previously described worked nicely. I was then able to
pressurise the system, and leave it for 48 hours to check that there was
no drop off in pressure.


--
Cheers,

John.

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